The state budget for the fiscal year that begins Oct. 1 mandates the study. The budget requires the Michigan Department of Transportation to submit a report to the Legislature by May 1, 2015.

"I would characterize this as the first step to even determine the viability/feasibility of such a service, and by no mean does this mean that we're going to see rail passenger service running between these communities in any time frame," Tim Hoeffner, director of the department's Office of Rail, told the Lansing State Journal (http://on.lsj.com/1nldPS8 ).

The department likely will hire a consultant to study socioeconomics in the communities along the route and how people move between the cities to help determine potential ridership, Hoeffner said.

It would take "many, many years" and an allocation from the Legislature to build the line, Hoeffner said.

Dan Sommerville of the Michigan Environmental Council said the route could be a natural choice for people looking for alternatives to road travel.

"Essentially, Detroit and Grand Rapids are the two largest metropolitan areas in the state, and right in the middle of that is our state capitol, and the only mode of transportation between those is a highway," Sommerville said.

More than a dozen colleges and universities are within walking distance along the proposed route, Sommerville said. He said that gives the line a solid source of passengers as students travel home from college or among schools.

"This could be something that helps stem that brain drain and keep young people here," he said.

Passenger rail travel has been increasing in Michigan, according to the state. Amtrak lines in Michigan had 589,142 passengers in 1994 and 795,996 passengers in 2013, the state said.